The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Travertine

The photo above shows travertine covering the outside surface of the J. Paul Getty Museum in Los Angeles, California. In this close-up, you can clearly see leaf fossils, evidence of the shallow water environment in which the travertine formed. Rainwater becomes acidic when it absorbs carbon dioxide (CO2) from the air. As this rainwater seeps into the ground, it dissolves the calcite in limestone layers. If this water should make its way back to the surface, bubbling up from a spring, for example, the saturated groundwater would release the CO2 and precipitate the calcite around algal mats, bacteria and even leaves.

The travertine of the Getty Museum comes from the most famous travertine quarry in the world, the Bagni di Tivoli, which is located east of Rome, Italy. It's the same travertine used to build the Coliseum, the Trevi Fountain and the colonnade of Saint Peter's Basilica. This rock started forming approximately 80,000 years ago -- the quarry has been active for about the last 2,000 years. Typically, travertine is cut across the bedding planes, revealing the layering of the rock. Travertine is lighter than granite, easier to cut, and capable of carrying heavy loads. Richard Meier, the architect for the Getty Museum, didn’t need the rock to bear great weights. He chose instead to highlight the wonderful texture of the rock, so he had the rock cut parallel to the bedding planes. As a result, when visiting the Getty Museum, one is able to admire the intricate texture and abundant fossils preserved in an ancient Roman spring. Photo taken on November 13, 2011.